1. Field of the Invention
The present invention relates to cutting tools, and more particularly, to a method for extending the life of cutting tools having one or more cutting edges through shot peening.
2. Description of the Prior Art
Cutting tools are a necessary staple of the vast majority of manufacturing and repair facilities in operation today. While cutting tools, in the broadest sense, encompass such devices as grinding wheels, gas torch cutters, laser beam cutters and the like, the present invention is directed toward cutting tools that have one or more cutting edges, especially those that are designed for use in machines such as drills, drill presses, mills, lathes and the like. Representative examples of such cutting tools include drill bits, taps, mill cutters, broaches, turning cutters, form cutters and the like.
The important characteristic which is common to all of these cutting tools is that their cutting edges must be sharp and must be maintained sharp in order to satisfactorily function in their designed application. As the cutting edges begin to dull, a variety of problems evolve. For example, a sequence of smooth cuts is gradually replaced with jagged and scored surfaced cuts. Dullness increases the friction forces between the tool and the workpiece, increasing the strain on the cutting machine, as well as increasing the heat of both the cutting tool and the workpiece, both of which become increasingly more susceptible to breakage. As the cutting chips and shavings become more irregular, jams and sticking of the tool increases. The combination of the increased torque forces and the work hardening brittleness to which a dull cutting tool is exposed will quickly lead to complete tool failure. Scratches on a dull cutting tool turn into cracks and eventual complete tool failure. Finally, as the cutting tool dulls, the quality of the workpiece decreases, since dimensional tolerances become increasingly difficult to hold.
Because of the expense and poor quality resulting from the above problems, a constant vigilence is required to maintain the cutting edges of cutting tools sharp. Typically, as the cutting tool begins to dull, it is removed and precision ground to restore sharp cutting edges. While this is a costly operation, including either machine down time or the expense of an inventory of backup tools to minimize machine down time, it is less costly than poor quality workpieces and the replacement of expensive broken cutting tools. Consequently, extending the life of cutting tools, including the time between required resharpening operations, is an everpresent goal. Although modern technology has provided improved alloys for high speed and tool steel cutting tools, further improvement, especially at low cost, would be of significant value.